About 5 decades have passed since the concept of moyamoya disease (MMD) was established in Japan. In that time, many clinical MMD studies have been performed from several different points of view, such as epidemiology, pathophysiology, surgical procedures, and prognosis. In addition, rapid developments in MMD genetic analysis have occurred. In light of all this activity, clinicians must continually update their knowledge of MMD in order to improve the prognosis of MMD patients. In this review article, we summarize the clinical MMD studies and introduce cutting-edge findings regarding MMD.